The functionality and performance of VMware ESX and ESXi are the same; the difference between the two hypervisors resides in their architecture and operational management. VMware ESXi is the latest hypervisor architecture from VMware. It has an ultra thin Linux kernel footprint with no reliance on a general-purpose OS, setting a new bar for security and reliability. The small footprint and hardware-like reliability of VMware ESXi enable it to also be available preinstalled on industry standard x86 servers.
ESXi Server is also available as a no-cost entry level hypervisor. During my deployment of ESXi Server I found a lack of available information on when ESXi Server is free and at what point ESXi Server incurs a license fee. Even internal VMWare personnel were unclear about the differentiation between an ESXi no-cost option versus ESXi Server available on a license fee basis.
One can download ESXi Server for a 60 day evaluation trial period. The 60 day trial provides one with a restricted function ESXi Server. It is not always clear what features are restricted, however during my use it appears that functions relating to cloning and backing up of virtual machines are indeed restricted. One can register their no-cost ESXi Server license to ensure one has a working ESXi Server longer than 60 days, however the functions relating to cloning and backup are still restricted. The functions relating to cloning and backup appear to only be available once one licenses a VMWare product, such as VSphere Essentials, which includes what is referred to a VMWare Consolidated Backup (VCB).
The VI Client is a desktop application used to communicate with ESXi Server. The VI Client can be used to configure an ESXi Server, monitor ESXi Server performance and take snapshot backups, however VI Client cannot easily be used to backup a virtual machine outside of a single ESXi Server environment. With the VI Client, the best backup one can hope to achieve is taking a snapshot backup to an alternate hard drive, also attached to the same ESXi Server. ESXi Server backups will be explorer in detail in another blog post.
Other available interfaces for managing the ESXi Server include the VI Command Level interface, essentially a batch like command level interface; commands being issued from a PC to the ESXi Server.
A Secure Shell (SSH) interface can also be enabledvia the ESXi console. Once enabled, programs like PuTTY and WinSCP can be used to communicate with the ESXi Server. SSH is available for diagnostic purposes (in theory), however I found the SSH interface to be essential for a stable on-going ESXi Server environment. I have found PuTTY necessary for monitoring the Linux based file system. I have had problems where the Linux based file system will fill up due to ESXi log file usage. I have to login via PuTTY and move log file out of the base Linux file system using either Linux commands or WinSCP. Once the Linux based file system starts filling up the ESXi Server will either become quite sluggish or an unexpected re-boots may occur.
In summary, I find essential single ESXi Server management tools to be VI Client, PuTTY and WinSCP. With SSH enabled, I had very little use for the VI Client command level interface. Having SSH enabled allows me to use PuTTY for what is essentially ESXi Server console access. I can issue Linux commands and ESXi Server specific commands directly.